Bordetellae:[unreadable] [unreadable] Bordetellae are Gram-negative bacilli causing respiratory tract infections of mammals and birds. Clinically important are B. pertussis, B. parapertussis and B. bronchiseptica. B. pertussis vaccines have been successful in preventing pertussis in infants and children. Veterinary vaccines against B. bronchiseptica are available, but their efficacy and mode of action are not established. There is no vaccine against B. parapertussis. Based on the concept that immunity to non-capsulated Gram-negative bacteria may be conferred by serum IgG anti-LPS we studied chemical, serological and immunological properties of the O-specific polysaccharides (O-SP) of B. bronchiseptica and B. parapertussis obtained by different degradation procedures. One type of the B. parapertussis and two types of B. bronchiseptica O-SP were recognized based on their non-reducing end saccharide structure; no cross-reaction between the two B. bronchiseptica types was observed. Competitive inhibition assays showed the immunodominance of the non-reducing end of these O-SP. Conjugates of B. bronchiseptica and B. parapertussis O-SP were prepared by using the Kdo residue exposed by mild acid hydrolysis of the LPS or the core glucosamine residue exposed by deamination of the LPS, for binding to an aminooxylated protein. Both coupling methods were carried out at a neutral pH, room temperature, and in a short time. All conjugates, injected into mice as saline solutions, at a fraction of an estimated human dose, induced antibodies to the homologous O-SP. These methodologies can be applied to prepare LPS-based vaccines against other Gram-negative bacteria.[unreadable] The protection afforded by licensed subunit pertussis vaccines is incomplete on an individual basis, likely due to the lack of direct bactericidal effect of anti toxin antibodies. However herd immunity, that occurs with wide vaccine uasage, provides the almost complete protection. An additinal vaccine component inducing bactericidal antibodies such as anti LPS, could increase vaccine efficacy on an individual basis. To that end B. pertussis and B. bronchiseptica LPS were isolated and analyzed. B. pertusis expresses only the core region saccharide (OS) composed of 12 sugars. B. bronchiseptica, easier cultured and with better yields, expresses LPS with almost identical core structure to that of B. pertussis, though we observed small variations: (1) the methylation of Fuc4NMe, 100% in B. pertussis is only 50% in B. bronchiseptica; (2) Hep is phosphorylated in about 30% in B. bronchiseptica,, while in B. petrussis it is not phosphorylated. B. bronchispetica LPS is mostly further substituted by O-specific chains (O-SP). For this study only a free core fraction, with no O-SP was used. Conjugates of both B. pertussis OS and B. bronchiseptica core were prepared by reacting their reducing-end Kdo moieties with an aminooxy linker bound to BSA. Both conjugates incorporated an average of 10 saccharide chains per BSA molecule, both reacted with anti-B. pertussis and anti-BSA sera with a line of identity and both were immunogenic in mice inducing similar antibody levels, measured by ELISA.